Motor back electromotive force automatic bleeder circuit and swing type quick pass gate

Abstract

The utility model relates to the technical field of motors, in particular to a motor back electromotive force automatic bleeder circuit and a swing type quick pass gate. According to the utility model, through arranging the passive back electromotive force discharge unit and the unidirectional conduction unit, when the motor generates back electromotive force, automatic conduction of the back electromotive force discharge unit and automatic cut-off of the unidirectional conduction unit are realized, thereby realizing automatic discharge of the back electromotive force, stably protecting a single-board device from being damaged by the back electromotive force of the motor, and prolonging the service life of the single-board device. Fixed and universal device type selection is realized and is not influenced by a motor type and a voltage withstanding value of a single-board device; and meanwhile, the equipment can still discharge back electromotive force under the condition of power failure, so that the single board is protected.

Description

Technical Field

[0001] The utility model relates to the technical field of motors, in particular to an automatic discharge circuit for back electromotive force of a motor and a swing-type fast-passing door. Background Art

[0002] Swing-type fast-pass doors are increasingly used in today's society. The environment is becoming more and more complex, and people rushing through the gate machine occurs from time to time. The swing door of the gate machine is controlled by a motor. During normal operation, the MCU controls the motor to rotate, thereby driving the door wing to open and close the door. However, in some abnormal situations where people rush through the gate machine, the door wing is driven to rotate by external force after being hit. At this time, the motor is driven by the door wing to rotate together. Due to the action of external force, the motor will become a generator and input back electromotive force into the inside of the single board in the reverse direction. When the single board is not adequately protected, it is easy to cause damage to the single board.

[0003] In the prior art, a commonly used technical solution is to connect a voltage stabilizing device in the circuit to achieve protection against the back electromotive force generated by the motor; in other technical solutions, a voltage monitoring unit is introduced to monitor the back electromotive force generated by the motor and electronically control the discharge to prevent the back electromotive force from causing damage to the upper circuit.

[0004] However, there are at least the following shortcomings in the prior art: the specifications of the voltage stabilizing device need to match the voltage withstand specifications of the chips and devices in the circuit, but it is often not easy to select, and high-voltage withstand devices that match the device selection will introduce higher hardware and design costs; the technical solution for voltage monitoring requires continuous power supply to the MCU, which is not available when the power is off, and cannot solve the problem that back electromotive force will still be generated when the motor is powered off. Utility Model Content

[0005] The utility model provides a motor back electromotive force automatic discharge circuit and a swing-type speed-pass gate, which are used to realize the motor back electromotive force discharge and single-board protection in the speed-pass gate motor with low cost.

[0006] The utility model provides a motor back electromotive force automatic discharge circuit, comprising:

[0007] Three-phase bridge circuit, back electromotive force discharge unit and unidirectional conduction unit, wherein:

[0008] The three-phase bridge circuit is electrically connected to the motor and is used to supply power to the motor;

[0009] The back electromotive force discharge unit is electrically connected to the motor and is used to discharge the back electromotive force generated by the motor;

[0010] The one-way conducting unit comprises a first end and a second end, wherein the first end of the one-way conducting unit is electrically connected to the three-phase bridge circuit, and the second end is electrically connected to the bus, and is used to cut off the electrical connection between the three-phase bridge circuit and the bus when the motor generates back electromotive force.

[0011] According to the automatic discharge circuit of the motor back electromotive force of the utility model, the back electromotive force discharge unit includes a P-channel MOSFET field effect tube and a discharge resistor, the gate of the P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the U-phase, V-phase, and W-phase power supply terminals of the motor, and the drain is electrically connected to the discharge resistor; the discharge resistor is grounded.

[0012] According to the motor back electromotive force automatic discharge circuit of the utility model, the turn-on voltage of the P-channel MOSFET field effect tube is not greater than a preset voltage.

[0013] According to the motor back electromotive force automatic discharge circuit of the utility model, the resistance value of the discharge resistor is smaller than the preset resistance value.

[0014] According to the motor back electromotive force automatic discharge circuit of the utility model, the one-way conducting unit is a diode, the cathode of the diode is electrically connected to the three-phase bridge circuit, and the anode is electrically connected to the busbar.

[0015] According to the motor back electromotive force automatic discharge circuit of the utility model, the back electromotive force discharge unit includes a U back electromotive force discharge unit, a V back electromotive force discharge unit, and a W back electromotive force discharge unit, wherein:

[0016] The U phase back electromotive force discharge unit is electrically connected to the U phase power supply terminal of the motor, and is used to discharge the back electromotive force generated by the motor in the U phase;

[0017] The V-phase back electromotive force discharge unit is electrically connected to the V-phase power supply terminal of the motor and is used to discharge the back electromotive force generated by the motor in the V-phase;

[0018] The W-phase back electromotive force discharge unit is electrically connected to the W-phase power supply terminal of the motor and is used to discharge the back electromotive force generated by the motor in the W-phase.

[0019] According to the motor back electromotive force automatic discharge circuit of the utility model, the U back electromotive force discharge unit includes a first P-channel MOSFET field effect tube and a first discharge resistor, the gate of the first P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the U-phase power supply end of the motor, and the drain is electrically connected to the first discharge resistor; the V back electromotive force discharge unit includes a second P-channel MOSFET field effect tube and a second discharge resistor, the gate of the second P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the V-phase power supply end of the motor, and the drain is electrically connected to the second discharge resistor; the W back electromotive force discharge unit includes a third P-channel MOSFET field effect tube and a third discharge resistor, the gate of the third P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the W-phase power supply end of the motor, and the drain is electrically connected to the third discharge resistor;

[0020] The first discharge resistor, the second discharge resistor and the third discharge resistor are grounded.

[0021] According to the motor back electromotive force automatic discharge circuit of the utility model, the first discharge resistor, the second discharge resistor and the third discharge resistor have the same resistance value; the turn-on voltage of the first P-channel MOSFET field effect tube, the second P-channel MOSFET field effect tube and the third P-channel MOSFET field effect tube is not greater than the preset voltage.

[0022] According to the motor back electromotive force automatic discharge circuit of the utility model, the one-way conducting unit includes a U-phase one-way conducting unit, a V-phase one-way conducting unit, and a W-phase one-way conducting unit. The first end of the U-phase one-way conducting unit is electrically connected to the U-phase power supply circuit of the three-phase bridge circuit, the first end of the V-phase one-way conducting unit is electrically connected to the V-phase power supply circuit of the three-phase bridge circuit, and the first end of the W-phase one-way conducting unit is electrically connected to the W-phase power supply circuit of the three-phase bridge circuit; the second ends of the U-phase one-way conducting unit, the V-phase one-way conducting unit, and the W-phase one-way conducting unit are all electrically connected to the bus.

[0023] The utility model also provides a swing-type speed-pass door, comprising a motor and a motor control circuit, wherein the motor control circuit comprises the motor back electromotive force automatic discharge circuit provided by the utility model.

[0024] The utility model provides an automatic motor back-electromotive force discharge circuit and a swing-type fast-pass gate. By setting a passive back-electromotive force discharge unit and a unidirectional conduction unit, when the motor generates a back-electromotive force, the back-electromotive force discharge unit is automatically turned on and the unidirectional conduction unit is automatically cut off, thereby realizing automatic discharge of the back-electromotive force, being able to stably protect single-board devices from being damaged by the motor back-electromotive force, realizing fixed and universal device selection, and being unaffected by the motor model and the withstand voltage value of the single-board devices; at the same time, the equipment can still discharge the back-electromotive force in the case of power failure to protect the single board. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 It is a structural schematic diagram of the motor back electromotive force automatic discharge circuit provided by the utility model;

[0027] Figure 2 The utility model provides a U-phase motor control circuit structure schematic diagram of a motor back electromotive force automatic discharge circuit. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the utility model clearer, the technical solution of the utility model will be described clearly and completely in conjunction with the drawings in the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0029] Combine the following Figure 1-Figure 2 The utility model describes a motor back electromotive force automatic discharge circuit and a swing-type fast-pass door.

[0030] Figure 1 Schematic diagram of the structure of the motor back electromotive force automatic discharge circuit of the utility model embodiment, such as Figure 1 As shown, it includes a three-phase bridge circuit 110, a back electromotive force discharge unit 120 and a unidirectional conduction unit 130, wherein:

[0031] The three-phase bridge circuit 110 is electrically connected to the motor and is used to supply power to the motor;

[0032] The back electromotive force discharge unit 120 is electrically connected to the motor and is used to discharge the back electromotive force generated by the motor; the back electromotive force discharge unit 120 is also electrically connected to the bus;

[0033] The one-way conducting unit 130 includes a first end and a second end. The first end of the one-way conducting unit 130 is electrically connected to the three-phase bridge circuit, and the second end is electrically connected to the bus, and is used to cut off the electrical connection between the three-phase bridge circuit 110 and the bus when the motor generates back electromotive force.

[0034] In the embodiment of the utility model, the motor may be a brushless DC motor.

[0035] In the embodiment of the utility model, the three-phase bridge circuit can be a MOS-based bridge circuit, or a switch circuit, a diode or other form of circuit for converting direct current into a three-phase power supply for a motor; in the embodiment of the utility model, when the motor is working normally, the unidirectional conduction unit is turned on, and the three-phase bridge circuit controls the current input of the motor through the signal transmitted by the bus to realize the operation of the motor; when the motor generates a back electromotive force due to the action of external force, the unidirectional conduction unit cuts off the electrical connection between the three-phase bridge circuit and the bus, so that the back electromotive force cannot be transmitted to the bus through the three-phase bridge circuit, thereby avoiding the back electromotive force from burning the single board; at the same time, the back electromotive force discharge unit is turned on to discharge the back electromotive force generated by the motor, actively consumes the energy of the motor back electromotive force, and ensures the safety of the motor and the single board.

[0036] In an embodiment of the utility model, the back-electromotive force discharge unit may include a circuit that can consume electrical energy formed by a capacitor, a resistor and a combination thereof. It can be understood that any set of back-electromotive force discharge units that can consume electrical energy can achieve the technical effect of discharging the back-electromotive force generated by the motor in the utility model and actively consuming the energy of the motor's back-electromotive force.

[0037] In the embodiment of the utility model, the unidirectional conduction unit can be a diode, or a circuit structure designed based on a diode, a thyristor, a field effect transistor or other electronic components to realize unidirectional conduction of current. The unidirectional conduction unit of the embodiment of the utility model is configured to conduct unidirectionally from the second end to the first end, that is, it is turned on when the electromotive force of the second end is higher than the electromotive force of the first end, and it is cut off when the electromotive force of the first end is higher than the electromotive force of the second end, so as to automatically cut off the electrical connection between the three-phase bridge circuit and the bus when the back electromotive force is generated, so that the back electromotive force cannot be transmitted to the bus through the three-phase bridge circuit, and cannot affect the subsequent circuits on the bus, thereby protecting the single board. It can be understood that the unidirectional conduction unit in the embodiment of the utility model can also be an electrically controlled switch with independent power supply or integrated power supply, which cuts off the electrical connection between the three-phase bridge circuit and the bus when the generation of the back electromotive force is detected, thereby protecting the single board.

[0038] In an embodiment of the utility model, the back electromotive force discharge unit includes a P-channel MOSFET field effect tube and a discharge resistor, the gate of the P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the motor, and the drain is electrically connected to the discharge resistor; the discharge resistor is grounded.

[0039] When the motor generates back electromotive force, the source voltage of the P-channel MOSFET field effect tube increases, and after reaching the turn-on voltage, the P-channel MOSFET field effect tube is turned on, and the back electromotive force is discharged to the ground through the discharge resistor, thereby realizing the discharge of the back electromotive force; after the discharge is completed, the source voltage of the P-channel MOSFET field effect tube decreases, the P-channel MOSFET field effect tube is cut off, and the motor resumes normal operation. Therefore, the utility model automatically switches to the normal working mode after the back electromotive force discharge is completed through the structure of the above-mentioned back electromotive force discharge unit, so that the motor runs more smoothly.

[0040] In the embodiment of the utility model, the resistance of the discharge resistor is less than the preset resistance. The utility model embodiment increases the discharge power by setting a smaller discharge resistor resistance, thereby increasing the discharge speed and reducing the influence time of the back electromotive force on the motor operation.

[0041] In the embodiment of the utility model, the turn-on voltage of the P-channel MOSFET field effect tube is not greater than a preset voltage; the preset voltage can be set according to circuit parameters. In the embodiment of the utility model, the sensitivity of back electromotive force discharge can be adjusted by adjusting the turn-on voltage of the P-channel MOSFET field effect tube. The smaller the turn-on voltage, the higher the sensitivity of back electromotive force detection and discharge.

[0042] In the embodiment of the utility model, the unidirectional conduction unit is a diode, the cathode of the diode is electrically connected to the three-phase bridge circuit, and the anode is electrically connected to the bus. When the back electromotive force is generated, the cathode voltage of the diode is greater than the anode voltage, and the diode is automatically cut off to prevent the back electromotive force from being transmitted to the bus. In the embodiment of the utility model, when the motor generates the back electromotive force by setting the diode, it can be cut off even if the motor is in the power-off state, and the single-board device can be stably protected from being damaged by the back electromotive force of the motor, and a fixed and universal device selection is realized, which is not affected by the motor model and the withstand voltage value of the single-board device.

[0043] Therefore, the automatic discharge circuit of the motor back-electromotive force provided by the utility model, by setting a passive back-electromotive force discharge unit and a unidirectional conduction unit, when the motor generates back-electromotive force, the back-electromotive force discharge unit is automatically turned on and the unidirectional conduction unit is automatically cut off, thereby realizing automatic discharge of the back-electromotive force, and can stably protect the single-board devices from being damaged by the motor back-electromotive force, realize fixed and universal device selection, and is not affected by the motor model and the withstand voltage value of the single-board devices; at the same time, the equipment can still discharge the back-electromotive force in the case of power failure to protect the single board.

[0044] Figure 2 It is a schematic diagram of the structure of the U-phase motor control circuit of the motor back electromotive force automatic discharge circuit of the embodiment of the utility model. The V-phase motor control circuit and the W-phase motor control circuit of the embodiment of the utility model can be correspondingly arranged according to the U-phase motor control circuit.

[0045] like Figure 2 As shown, the U-phase motor control circuit includes a high-level rectifier resistor R1, a low-level rectifier resistor R2, R7, N-channel MOSFET field effect tubes Q1, Q2, a diode D1, a P-channel MOSFET field effect tube Q10, and a voltage discharge resistor R10; wherein: the high-level rectifier resistor R1, the low-level rectifier resistor R2, R7, and the N-channel MOSFET field effect tubes Q1, Q2 together constitute a U-phase rectifier circuit for powering the U-phase of the brushless DC motor; the back electromotive force discharge unit includes a P-channel MOSFET field effect tube Q10 and a discharge resistor R10, the gate of the P-channel MOSFET field effect tube Q10 is electrically connected to the bus, the source is electrically connected to the U-phase power supply end of the motor, and the drain is connected to the discharge resistor R10; the discharge resistor R10 is grounded.

[0046] When the motor works normally, the cathode voltage of the diode D1 is less than the anode voltage, that is, the diode D1 is turned on, the source voltage of the P-channel MOSFET field effect tube Q10 is VM or 0, the gate voltage is VM, and the back electromotive force discharge unit does not work;

[0047] When the motor generates back electromotive force, the cathode voltage of the diode D1 is greater than the anode voltage, that is, the diode D1 is automatically cut off, and the source voltage of the P-channel MOSFET field effect tube Q10 increases. After reaching the turn-on voltage, the P-channel MOSFET field effect tube Q10 is turned on, and the back electromotive force is discharged to the ground through the discharge resistor R10, thereby realizing the discharge of the back electromotive force; after the discharge is completed, the source voltage of the P-channel MOSFET field effect tube Q10 decreases, the P-channel MOSFET field effect tube Q10 is cut off, and the motor resumes normal operation.

[0048] In the embodiment of the utility model, the back electromotive force discharge unit can be electrically connected to the power supply end of one phase of the motor, or it can be electrically connected to the power supply ends of multiple phases of the motor; it can be understood that the power supply end of each phase of the motor needs to be electrically connected to at least one back electromotive force discharge unit, so as to discharge the back electromotive force through the back electromotive force discharge unit; the unidirectional conduction unit can be electrically connected to the three-phase bridge circuit of one phase of the motor, or it can be electrically connected to the three-phase bridge circuit of multiple phases of the motor; the three-phase bridge circuit of each phase of the motor needs to correspond to at least one unidirectional conduction unit to achieve automatic cutoff when the back electromotive force is generated;

[0049] In an embodiment of the utility model, when the back-electromotive force discharge unit is electrically connected to the power supply ends of multiple phases of the motor, specifically, the back-electromotive force discharge unit includes a P-channel MOSFET field effect tube and a discharge resistor, the gate of the P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the U-phase, V-phase, and W-phase power supply ends of the motor, and the drain is electrically connected to the discharge resistor; the discharge resistor is grounded; at this time, using a P-channel MOSFET field effect tube and a discharge resistor to form a back-electromotive force discharge unit can cope with the back-electromotive force generated by the U-phase, V-phase, and W-phase, saving hardware costs.

[0050] In another preferred embodiment of the utility model, when the back electromotive force discharge unit is electrically connected to the power supply end of one phase of the motor, specifically, the back electromotive force discharge unit includes a U back electromotive force discharge unit, a V back electromotive force discharge unit, and a W back electromotive force discharge unit, wherein:

[0051] The U phase back electromotive force discharge unit is electrically connected to the U phase power supply terminal of the motor, and is used to discharge the back electromotive force generated by the motor in the U phase;

[0052] The V-phase back electromotive force discharge unit is electrically connected to the V-phase power supply terminal of the motor and is used to discharge the back electromotive force generated by the motor in the V-phase;

[0053] The W-phase back electromotive force discharge unit is electrically connected to the W-phase power supply terminal of the motor and is used to discharge the back electromotive force generated by the motor in the W-phase.

[0054] The U back electromotive force discharge unit includes a first P-channel MOSFET field effect tube and a first discharge resistor, wherein the gate of the first P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the U-phase power supply terminal of the motor, and the drain is electrically connected to the first discharge resistor; the V back electromotive force discharge unit includes a second P-channel MOSFET field effect tube and a second discharge resistor, wherein the gate of the second P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the V-phase power supply terminal of the motor, and the drain is electrically connected to the second discharge resistor; the W back electromotive force discharge unit includes a third P-channel MOSFET field effect tube and a third discharge resistor, wherein the gate of the third P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the W-phase power supply terminal of the motor, and the drain is electrically connected to the third discharge resistor;

[0055] The first discharge resistor, the second discharge resistor and the third discharge resistor are grounded.

[0056] In the embodiment of the utility model, different back-electromotive force discharge units are arranged to correspond one to one with different phases of the motor, so that each power supply phase of the motor corresponds to an independent back-electromotive force discharge unit, and the generation of back-electromotive force in any phase will not affect the operation of other phases.

[0057] In the embodiment of the utility model, the first discharge resistor, the second discharge resistor, and the third discharge resistor have the same resistance value, and the resistance values ​​of the first discharge resistor, the second discharge resistor, and the third discharge resistor are less than the preset resistance value. In the embodiment of the utility model, each back electromotive force discharge unit of the motor is symmetrically arranged so that the motor can run smoothly.

[0058] In an embodiment of the utility model, the one-way conducting unit includes a U-phase one-way conducting unit, a V-phase one-way conducting unit, and a W-phase one-way conducting unit. The first end of the U-phase one-way conducting unit is electrically connected to the U-phase power supply circuit of the three-phase bridge circuit, the first end of the V-phase one-way conducting unit is electrically connected to the V-phase power supply circuit of the three-phase bridge circuit, and the first end of the W-phase one-way conducting unit is electrically connected to the W-phase power supply circuit of the three-phase bridge circuit; the second ends of the U-phase one-way conducting unit, the V-phase one-way conducting unit, and the W-phase one-way conducting unit are all electrically connected to the bus.

[0059] The embodiment of the utility model sets different unidirectional conduction units corresponding to different phase power supplies of the motor, so that each power supply phase of the motor corresponds to an independent unidirectional conduction unit, so that when the unidirectional conduction unit of any phase is cut off, it will not affect the power supply of other phases, so that the motor can run smoothly.

[0060] It can be seen that the automatic discharge circuit of the motor back-EMF provided by the utility model, by setting a passive back-EMF discharge unit and a unidirectional conduction unit, can realize the automatic discharge of the back-EMF by automatically turning on the back-EMF discharge unit and automatically cutting off the unidirectional conduction unit when the motor generates back-EMF, thereby realizing the automatic discharge of the back-EMF, and can stably protect the single-board devices from being damaged by the motor back-EMF, realize fixed and universal device selection, and is not affected by the motor model and the withstand voltage value of the single-board devices; at the same time, the equipment can still discharge the back-EMF in the case of power failure to protect the single board.

[0061] The utility model also provides a swing-type speed-pass door, comprising a motor and a motor control circuit, wherein the motor control circuit comprises a motor back electromotive force automatic discharge circuit provided according to an embodiment of the utility model.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the utility model.

Claims

1. A motor back electromotive force automatic discharge circuit, characterized in that: include: Three-phase bridge circuit, back electromotive force discharge unit and unidirectional conduction unit, wherein: The three-phase bridge circuit is electrically connected to the motor and is used to supply power to the motor; The back electromotive force discharge unit is electrically connected to the motor and is used to discharge the back electromotive force generated by the motor; the back electromotive force discharge unit is also electrically connected to the bus; The one-way conducting unit comprises a first end and a second end, wherein the first end of the one-way conducting unit is electrically connected to the three-phase bridge circuit, and the second end is electrically connected to the bus, and is used to cut off the electrical connection between the three-phase bridge circuit and the bus when the motor generates back electromotive force.

2. The motor back electromotive force automatic discharge circuit according to claim 1, characterized in that: The back electromotive force discharge unit includes a P-channel MOSFET field effect tube and a discharge resistor, the gate of the P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the U-phase, V-phase, and W-phase power supply terminals of the motor, and the drain is electrically connected to the discharge resistor; the discharge resistor is grounded.

3. The motor back electromotive force automatic discharge circuit according to claim 2, characterized in that: The turn-on voltage of the P-channel MOSFET field effect tube is not greater than a preset voltage.

4. The motor back electromotive force automatic discharge circuit according to claim 2, characterized in that: The resistance of the discharge resistor is less than a preset resistance.

5. The motor back electromotive force automatic discharge circuit according to claim 1, characterized in that: The one-way conducting unit is a diode, a cathode of the diode is electrically connected to the three-phase bridge circuit, and an anode of the diode is electrically connected to the busbar.

6. The motor back electromotive force automatic discharge circuit according to claim 1, characterized in that: The back electromotive force discharge unit includes a U back electromotive force discharge unit, a V back electromotive force discharge unit, and a W back electromotive force discharge unit, wherein: The U phase back electromotive force discharge unit is electrically connected to the U phase power supply terminal of the motor, and is used to discharge the back electromotive force generated by the motor in the U phase; The V-phase back electromotive force discharge unit is electrically connected to the V-phase power supply terminal of the motor and is used to discharge the back electromotive force generated by the motor in the V-phase; The W-phase back electromotive force discharge unit is electrically connected to the W-phase power supply terminal of the motor and is used to discharge the back electromotive force generated by the motor in the W-phase.

7. The motor back electromotive force automatic discharge circuit according to claim 6, characterized in that: The U back electromotive force discharge unit includes a first P-channel MOSFET field effect tube and a first discharge resistor, wherein the gate of the first P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the U-phase power supply terminal of the motor, and the drain is electrically connected to the first discharge resistor; the V back electromotive force discharge unit includes a second P-channel MOSFET field effect tube and a second discharge resistor, wherein the gate of the second P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the V-phase power supply terminal of the motor, and the drain is electrically connected to the second discharge resistor; the W back electromotive force discharge unit includes a third P-channel MOSFET field effect tube and a third discharge resistor, wherein the gate of the third P-channel MOSFET field effect tube is electrically connected to the bus, the source is electrically connected to the W-phase power supply terminal of the motor, and the drain is electrically connected to the third discharge resistor; The first discharge resistor, the second discharge resistor and the third discharge resistor are grounded.

8. The motor back electromotive force automatic discharge circuit according to claim 7, characterized in that: The first discharge resistor, the second discharge resistor, and the third discharge resistor have the same resistance value; the turn-on voltage of the first P-channel MOSFET field effect transistor, the second P-channel MOSFET field effect transistor, and the third P-channel MOSFET field effect transistor is not greater than a preset voltage.

9. The motor back electromotive force automatic discharge circuit according to claim 6, characterized in that: The one-way conducting unit includes a U-phase one-way conducting unit, a V-phase one-way conducting unit, and a W-phase one-way conducting unit. The first end of the U-phase one-way conducting unit is electrically connected to the U-phase power supply circuit of the three-phase bridge circuit, the first end of the V-phase one-way conducting unit is electrically connected to the V-phase power supply circuit of the three-phase bridge circuit, and the first end of the W-phase one-way conducting unit is electrically connected to the W-phase power supply circuit of the three-phase bridge circuit; the second ends of the U-phase one-way conducting unit, the V-phase one-way conducting unit, and the W-phase one-way conducting unit are all electrically connected to the bus.

10. A swing-type fast-pass door, characterized in that: It comprises a motor and a motor control circuit, wherein the motor control circuit comprises the motor back electromotive force automatic discharge circuit according to any one of claims 1-9.

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